# Symbols on Weather Maps

## Learning Goal 1f. Recognize and interpret certain weather and obscuration glyphs on weather charts.

Weather maps show locations of weather stations worldwide. Each weather station observes many weather variables (wind, temperature, clouds, weather, precipitation, etc). The issue: how to display so much info at so many locations on the same map? The solution: meteorologists devised symbols or glyphs as a short-hand notation for many of these weather variables.

In the tables below, the glyph is the symbol that is used on weather maps. Also listed for completeness is the text abbreviation for the same phenomenon, which is used in text-based Meteorological Aviation Reports (METARs). For this course, focus only on the glyphs.

For this learning goal we consider only a small sample of the glyphs used in meteorology.  There are many more that are not shown here, and for which you are NOT responsible to know for this course.  Please focus on only the key glyphs shown here.

### Weather and Storm Glyphs

The intensity of the precipitation is indicated by the number and arrangement of those glyphs, as described in Table 9-3b. Also, a descriptor for the precipitation can be included.  Here is just a subset of intensity and descriptor glyphs:

### Examples of Combinations of Glyphs

The glyphs described above can be combined in logical ways.  Here are some examples:

Glyphs
Meanings

.
Moderate-intensity drizzle
.
.
Moderate-intensity rain
.
.
Moderate-intensity snow

.
Rain shower   |   snow shower

Thunderstorm with rain   |   Thunderstorm with snow

Freezing drizzle    |    Freezing rain

Keywords: drizzle, rain, snow, heavy, light, moderate,  shower, thunderstorm, freezing, fog, haze, mist, smoke, sand, blowing

Extra info for Experts; Not Needed for this Course.

#### Explanation of "light", "moderate", and "heavy" precipitation

For rain, the intensity is given by how fast a bucket or rain gauge fills with rainwater, i.e. the increase in water depth per hour (e.g. mm/h). Table 7-3 gives the details.
For drizzle and snow, the intensity is given by how poor the visibility is. Visibility is how far you can see through the atmosphere, and is discussed in Learning Goal 9e. It is measured as a distance (e.g. km). Table 7-4 gives the details.

#### Cloud Glyphs

There are many cloud glyphs, so we will focus on the main ones here. Refer back to Learning Goal 9a to see photos of these clouds.

.

.

Practice Exercises for Experts (not needed for this Course)

Exercise (c) shows the symbol for intermittent moderate drizzle.
Exercise (s) shows the symbol for a light rain shower.
Exercise (ab) shows the symbol thunderstorm with snow.

While the above tables showed the general principles used to organize the weather-map symbols, here is a link that shows each specific symbol with an explanation of what it means
(Courtesy of the US National Center for Atmospheric Research. From http://weather.rap.ucar.edu/info/wxSymbols_anno1.pdf , downloaded on 24 May 2017.)